The present invention pertains to closures or lids for containers or drums provided for multiple use, including the containment of toxic waste or materials.
Such drum type containers are generally constructed of plastic, such as high density polyethylene, and they are corrosion resistant and have adequate mechanical strength combined with light weight such that they provide a light weight safe containment of hazardous or other materials without leaking, despite rough handling during transportation. Such containers when empty are also constructed to be stackable for space saving considerations.
Generally the plastic molded drums or containers in the range of from three gallon to fifty-five gallon capacity are provided with split ring metal chime clamps to facilitate the attachment of the lid to the container. These drums or containers are either employed as drum over packs for containing conventional metal drums therein filled with toxic materials, or they may be employed simply as containers for liquid or solid materials without the inclusion of a metal drum.
For most designs, the split ring clamp is provided with an annular inwardly facing groove that effects a deforming securement of the rim of the lid to the top or neck of the drum wall.
To assure a secured retention of the lid, designs for the lid securing structures are tested. For examples, specifications have been provided by a variety of commercial, international and government entities and the United States Department of Transportation (DOT), Research and Special Programs Administration. However, the Untied Nations has also set specifications which are even more rigorous.
Typically, drop tests are called for by the test procedures wherein samples taken at random are filled with dry finely powdered or liquid material to an authorized net weight and closed as for use. The containers so filled with dry powder or water, must withstand drop tests of varying heights upon specified parts without leakage or serious rupture. In one such drop, the top chime is dropped diagonally directly onto solid concrete. In another test, the bottom of the container is dropped diagonally such that the bottom chime contacts solid concrete. The drop test heights vary but generally average from four to six feet.
While drum-lid assemblies including split clamping rings have met the specifications as above required, 100% reliance upon split ring clamping assemblies to hold the lid and drum assemblies together during such drop tests has proven to be inadequate when dealing with the larger drums approaching the 55 gallon or higher drum capacity range.
The plastic and closure combination described in U.S. Pat. No. 5,605,244 and issued to the present inventor, minimizes the reliance upon split ring clamping assemblies to hold the lid and drum together. However, it is a principal object of the present invention to provide a safe and reliable closure and container combination which completely eliminates the requirement of a split ring clamping assembly.